expire will set in_use to false

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -69,6 +69,7 @@ module ActiveRecord
         @visitor = nil
         @schema_cache = SchemaCache.new self
         @in_use = false
+        @last_use = false
       end
 
       def lease
@@ -80,6 +81,10 @@ module ActiveRecord
         end
       end
 
+      def expire
+        @in_use = false
+      end
+
       # Returns the human-readable name of the adapter. Use mixed case - one
       # can always use downcase if needed.
       def adapter_name

activerecord/test/cases/connection_adapters/abstract_adapter_test.rb

@@ -26,6 +26,13 @@ module ActiveRecord
         adapter.lease
         assert adapter.last_use
       end
+
+      def test_expire_mutates_in_use
+        assert adapter.lease, 'lease adapter'
+        assert adapter.in_use?, 'adapter is in use'
+        adapter.expire
+        assert !adapter.in_use?, 'adapter is in use'
+      end
     end
   end
 end